Corrosion protection inserts for metallic construction supports

ABSTRACT

An insert for construction supports such as joist hangars and hurricane straps provides corrosion protection from chemicals and moisture in exterior construction lumber. The insert is a semi-rigid body having a shape that fits the construction support so that surfaces of the insert are disposed between the support and the construction lumber at joints in the construction. In the preferred embodiments, the inserts are made of a plastic material and provide a chemical, moisture and electrical barrier between the support and exterior lumber elements of a structure.

This application claims the benefit of U.S. Provisional Application No. 60/925,740 filed Apr. 23, 2007.

FIELD OF THE INVENTION

The present invention relates to corrosion protection for metallic supports used in exterior treated wood construction, and more particularity, for protective inserts used with galvanized steel hangars, straps, brackets and supports.

BACKGROUND OF THE INVENTION

Steel hangars, straps, brackets and other reinforcing supports are often used in exterior and interior construction because of the increased strength, rigidity and safety these supports add to the structure. Supports used with lumber, especially exterior treated lumber are susceptible to corrosion due to moisture and corrosive chemicals often used to prevent rot and deterioration of the lumber.

Lumber treatment often utilizes metallic compounds, as well as acidic or caustic compounds, which can react chemically or electrically through galvanic corrosion to attack and degrade the steel supports. Moisture causes chemical compounds in the lumber to leach, further compounding the problem.

Corrosion-inhibiting methods have been used in the past to address the problem of accelerated corrosion of steel supports. These methods include use of highly corrosion resistant materials in the supports such as stainless steel. Although stainless steel reduces the corrosion due to chemical and galvanic attack, it is expensive and requires use of stainless steel fasteners such as screws and nails in order to be effective. Applying a layer of a highly anodic metal such as zinc is commonly used to protect the steel structure. Such galvanic corrosion-protection measures have been effective in the past, but are insufficient for new lumber treatments that include use of high metallic compound formulation, as well as corrosive biocides and fungicides.

U.S. Patent Application Publication No. 2005/0126109 discloses an anticorrosion separator for use with galvanized joist hangars. The separator is a membrane which separates the metal from wood to provide corrosion protection. The membrane must be applied to all wood surfaces in contact with the galvanized supports, requiring considerable time for fitting the membrane.

There exists a need for a method for protecting metallic supports from corrosion due to exterior lumber chemical and moisture attack which is simple, quick to use, and low in cost.

OBJECTS AND SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an insert for use with metallic construction supports such as joist hangars, hurricane straps and post supports which provide a barrier preventing the leeching of chemicals and moisture from treated wood to the supports.

Another object of the present invention is to provide an insert for use with metallic construction supports that provides electrical insulation between treated lumber and the support to reduce galvanic corrosion.

Another object of the present invention is to provide an insert for use with metallic construction supports that can be installed quickly and at low cost.

Still another object of the present invention is to provide method for protecting metallic construction supports from corrosion by providing a barrier between the support, treated lumber and fasteners used to attach the support to the lumber.

The method of the present invention is an insert disposed between a construction support, such as a joist hangar, hurricane strap or post supports and construction members such as treated wood joists and ledger boards, which prevents contact with, and provides a barrier to reduce corrosion of the support. The barrier may include a moisture, chemical and/or electrical barrier between the metallic support and the lumber. In still other embodiments, the barrier may insulate support fasteners from the support.

In the preferred embodiments, the insert is a semi-rigid polymeric structure, shaped to fit or otherwise engage the construction support so that when installed, the insert provides the barrier between the support and the treated lumber. The insert comprises at least two orthogonal faces or surfaces which are shaped to conform to corresponding surfaces on the construction support that attach to treated lumber surfaces attached by the support.

The insert may be mechanically attached to the support, or it may be installed between the support and the lumber during construction. In the preferred embodiments, the inserts are injection molded from high density polyethylene to provide good corrosion resistance and sufficient rigidity for ease of installation. The inserts may be shaped to “snap” into the supports so that the insert is between the support and lumber, providing an installation that is simple and fast.

Another embodiment of the invention attaches the “insert” by applying a resin to the support and then curing the resin to permanently bond the insert to the support. The cured resin provides the mechanical, moisture, chemical and electrical barrier properties to protect the support from corrosion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 is a plan view of an insert for use with a joist hangar;

FIG. 2 is a front elevation view of the insert of FIG. 1;

FIG. 3 is a side elevation drawing of the insert of FIG. 1;

FIG. 4 is a plan view of the insert of FIG. 1 showing installation in a joist hangar, shown in dotted lines, and the joist hanger insert of FIG. 1 between the joist hangar and a joist and ledger board joint shown in phantom lines;

FIG. 5 is a front elevation drawing of the insert of FIG. 4 showing installation between a joist hangar and a joist-ledger board joint;

FIG. 6 is a side elevation drawing of the insert of FIG. 4 showing installation between a joist hangar and a joist-ledger board joint;

FIG. 7 is a plan view of an alternative embodiment of the joist hangar insert of FIG. 1 having a slotted back plate to allow fitting with differing widths of joists and joist hangars;

FIG. 8 is a front elevation drawing of the insert of FIG. 7, and dotted lines of FIGS. 7 and 8 showing an alternative embodiment having sections of the joist hangar insert attached and spaced by joining strips;

FIG. 9 is a side elevation drawing of the insert of FIG. 7.

FIG. 10 is perspective drawing of an insert similar to the split joist hangar insert of FIGS. 7-9 fitting into a joist hangar and a joist fitting into the assembly;

FIG. 11 is a plan view of a post support insert;

FIG. 12 is a front elevation drawing of the post support insert of FIG. 1 with a post support shown in dotted lines and a post shown in phantom lines;

FIG. 13 is a side elevation drawing of the post support insert of FIG. 11;

FIG. 14 is a plan view of a construction strap insert attached to a construction strap by tabs or by aperture snap elements that engage the nail holes of the strap;

FIG. 15 is a front elevation drawing of the insert of FIG. 14;

FIG. 16 is a side elevation drawing of the insert of FIG. 14 showing an alternate pressure-sensitive adhesive strip for attachment to the construction strap;

FIG. 17 is a cross section of an alternative embodiment of the invention showing a construction strap with integral insert consisting of a coating of the strap formed by a cured resin; and

FIG. 18 is a cross section of the construction strap of FIG. 17 having an insert coating on the lumber contact sides of the strap.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a description of the preferred embodiments of corrosion protector inserts for exterior construction hangars and brackets.

FIGS. 1-3 are plan and front and side elevation drawings, respectively of a joist hangar insert 101 for corrosion protection of a joist hangar used in exterior construction, such for use on decks, porches and other exterior floor systems. FIGS. 4-6 are plan and front and side elevation drawings, respectively of joist hangar insert 101 installed in a typical exterior deck application and providing corrosion protection to joist hangar 401 attaching joist 403 to ledger plate 405.

Joist hangar insert 101 comprises a back plate 103, two side plates 105 and bottom plate 107. Insert 101 may be formed as a single piece such as by casting, injection molding or vacuum forming from a plastic film such as high density polyethylene, or it may be fabricated from individual pieces and bonded or welded by means known in the art.

Interior side plate spacing 109 is chosen to provide a fit with standard joist width or thickness measurements. For example, width 109 may be chosen to be approximately 1.5 inches to provide a fit with standard 2″ dimensional exterior treated lumber such as that used for porch or deck joists. In the preferred embodiments, the selected width 109 will provide a loose fit with a joist, even allowing for individual differences in lumber due to manufacturing tolerances, moisture levels and temperature. In the preferred embodiments, width 111 is chosen to provide a fit with the inside of standard joist hangars, such as joist hangar 401 of FIGS. 4-6. For example, width 111 may be chosen to provide a tight or interference fit with the inside joist width of a standard hangar, allowing retention of insert 101 in the hangar during joist installation and fastening operations.

In the preferred embodiments, insert width 112, insert depth 113, insert bottom depth 115, and insert height 117 are chosen to be at least equal to corresponding joist hangar dimensions so that full corrosion protection exists between joist the joist hangar and the corresponding deck members. In the more preferred embodiments, insert dimensions 112, 113, 115 and 117 are greater than the corresponding joist hangar dimensions in order to provide additional corrosion protection. For example, insert width 112 is chosen to be greater than joist hanger 401 width to provide insert width overlap 501 of FIG. 5. Similarly, insert depths 113, 115, and insert height 117 are chosen to provide respective width overlap 601 and height overlap 603 of FIG. 6. Inserts 101 may be made of several heights 117 to allow use with standard joist dimensions used in construction.

Insert 101 provides a physical barrier between the joint surfaces of joist hangar 101 and joist 403 and ledger plate 405. In the preferred embodiments, insert 101 is made of a material which provides both mechanical separation, a moisture and chemical barrier, and electrical insulation between joist hangar 401 and the treated lumber members (joist 403 and ledger board 405). In the preferred embodiments, insert 101 material provides good mechanical tensile, puncture and abrasion resistance.

FIGS. 7-9 are plan view and front and side elevation drawings, respectively of alternative embodiment 701 of joist hangar insert 101 for accommodating varying joist and joist hangar widths. Joint hangar insert 701 utilizes a slot 703 for providing additional adjustment of width 109 or 111 depending on the width of a joist such as joist 403 of FIG. 4. Slot 703 also allows an interference fit for inserting and retaining insert 701 in a joist hangar. Slot 703 may be a vertical through slot as shown in the figure, or it may extend only part way of the longitudinal height 117 of the insert. Slot 703 also provides a means to accommodate varying widths of the joist without utilizing different inserts. Slot 703 may also extend partially through bottom portion 107 to add additional flexibility to width adjustments.

In other embodiments, insert side portion joining strips 706, shown in dotted lines in the FIGS. 7-8, attach respective side portions 701A, 701B at a distance represented by slot 703 and 704 width. Strips 706, disposed on back portion 103 and bottom portion 107, allow sizing insert widths 109 and 111 for the maximum joist and hangar widths, respectively, and provide a means to adjust widths 109 and 111 for smaller width applications by “crushing” joining strips 706. Strips 706 also allow slight over sizing of width 111 so that insert 701 is retained in joist hangar 401 of FIGS. 4-6 by slight compression of sides 105 and bottom 107, before insertion in hangar 401 of FIGS. 4-6.

The springing effect of strips 706 retains insert 701 in the hangar, adding flexibility in component assembly. Joining strips 706 may be of various widths or thickness to allow the desired crushing effect. Joining strips 706 may be other forms, such as serrated or corrugated strips, or simply thinner sections of back portion 103 and bottom portion 107, allowing compression of the insert. Slot 708, between bottom portion 107 and back portion 103 provides a means for moisture drainage. Other apertures in bottom portion 107 may be added.

FIG. 10 is a perspective drawing of assembly of a joist hanger insert 1001 similar to the slotted insert of FIGS. 7-9. In one preferred method of use, insert 1001 is inserted inside of joist hangar 1003 before attaching joist hangar 1003 to ledger plate 1007 by fasteners (not shown). End 1002 of joist 1005 is then placed in insert 1001 and fasteners (not shown) used to fasten joist 1005 to hangar 1003. Alternatively, joist 1005 with insert 1003 installed may be fastened to hangar 1003 before fastened to ledger plate 1007.

FIGS. 11-13 are plan view and front and side elevation drawings, respectively of alternative embodiment of insert 1101 for use with post base supports such as post support 1111. Insert 1101 comprises a base portion 1103 and side portions 1105. Base and side dimensions of post support 1101 are selected to fit inside post support 1111 as shown in FIG. 12. Construction and use of post insert 1101 is similar to joist insert embodiments described earlier. Optional aperture 1107 may be used drainage of accumulated moisture.

FIGS. 14-16 are plan view and front and side elevation drawings, respectively of alternative embodiment of insert 1401 for use with strap supports such as “hurricane straps”. Elongated insert 1401 comprises a top portion 1403 connected to a bottom portion 1405 by connector portion 1407. Tabs 1409A, 1409B provide a means to attach or snap insert 1401 into the interior portion of hurricane strap 1402 as shown in FIG. 14. Tabs 1409A, 1409B may be “U” or J-shaped shaped cross section as shown in the figures, or they may be friction-type tabs such as L-shaped cross section tabs which utilize friction in of leg portion 1411 against the edge of the hangar.

In still other embodiments, button tabs such as button tabs 1413, shown on bottom portion 1405, provide engagement elements that engage apertures such as nail holes 1415 of hangar 1402. Other male/female or complementary engagement elements such as snap fittings may be used. Adhesives 1603, distributed on insert 1401 such as pressure sensitive coatings or tapes may be used to attach insert 1401 to the protected surfaces of hangar 1402. In still other embodiments, discrete clips such as “U” clips may be used to clamp insert 1401 to hangar 1402. These and other mechanical attachment methods may be used with any of the embodiments of the invention described herein.

The inserts of the embodiments described herein provide separation and a physical moisture, chemical and electrical barrier between treated lumber and contact surfaces of metallic structural hangars, straps and supports. They reduce corrosion of the hangars, straps and supports by preventing contact of the metallic elements of the supports to the corrosive compounds in the treated lumber. They reduce leeching of corrosive chemicals in the treated lumber to the metallic components. They also provide electrical insulation to reduce electrical currents, necessary for galvanic corrosion from flowing between the metallic structural components and fasteners and metallic compounds in the treated lumber.

The inserts of the present invention may be made from any polymeric material that provides the desired physical separation, moisture barrier, and electrical insulation properties desired in the inserts. High density polyethylene (HDPE) is a preferred material for making the inserts due to its good mechanical strength properties, electrical insulation properties, formability and low cost. In the preferred embodiments, the material properties and thickness provides sufficient rigidity so that interference or tight fits are possible with construction supports such as joist hangars. Other polyolefins such ultra-high density or linear density polyethylene, polypropylenes, polyvinyl chloride (PVC), fluoropolymers such as PTFE, and other commodity and engineered plastics. Structural fillers such as reinforcement fibers may be added to the resins used to provide additional strength and rigidity.

In the preferred embodiments, the inserts of the present invention are formed by casting or molding in forms, or fabricating from sheet material. A more preferred method of forming is injection molding, allowing accurate, low-cost manufacturing. In other embodiments, the inserts are vacuum formed or welded or bonded from sheet material. The inserts may also be formed as separate pieces, for example by separate halves 701A, 701B of FIG. 8. Or cuts can be made in the inserts after forming to provide overlapping of slit portions such as back portion 103 of FIGS. 1-9. Such slits provide the width adjustment features of slot 703 of FIGS. 7-9.

In the preferred embodiments, the thickness of the inserts is sufficient to provide adequate rigidity to allow insertion and retention in the structural hangar components, yet thin enough to prevent excessive separation from the lumber structural components and to reduce cost and weight of the inserts. In the preferred embodiments, the insert thickness is less than 0.125″. In the more preferred embodiments, the thickness of the inserts is less than 0.100″. In the still more preferred embodiments, the thickness of the inserts is less than 0.075″. In the most preferred embodiments, the thickness of the inserts is less than 0.050″. In some applications, the inset thickness may be 0.020″-0.040″ to minimize cost and clearance issues. Structural shape sections, such as integrally-cast ribs in the structures may also be used to increase rigidity of the insert structures.

Still another embodiment of the present invention utilizes application of the “insert” by dipping, spraying or brushing a polymeric resin on the structural component and curing the resin to form a bonded insert or coating on the structural component. FIG. 17 is a cross section of a coated structural strap 1701. The coated strap may utilize a conventional base portion 1703 such as the hurricane strap of FIGS. 14-16. The section is taken through a top portion showing nail holes 1705. In the preferred embodiments, coating 1707 is a cured polymeric resin coating all surfaces of base potion 1703 including the interior surfaces of hail holes 1705. Coating of nail holes 1705 reduces galvanic corrosion of fasteners such as nails or screws which would otherwise contact interior surfaces of the nail holes. Coating of the interior (non-lumber contacting) surfaces of strap 1703 also prevents direct contact of the nail or screw heads with metallic surfaces of strap 1703.

In the preferred embodiments, coating 1707 is a cured polymeric resin having good mechanical properties, good bond strength with the base portion material, good moisture barrier properties, and is electrically insulative. In the preferred embodiments, coating 1707 is applied in the uncured state by dipping, spraying or brushing, and cured after application. In the preferred embodiments, coating 1707 is an epoxy material. In other embodiments, coating 1707 is a polyester or other thermoset polymer. In still other embodiments, coating 1707 is a thermoplastic polymer.

FIG. 18 is an alternative embodiment 1801 of the coated strap 1703 of FIG. 16 having a coating 1807 covering only a portion of strap 1703. In the preferred embodiments, coating 1807 covers only the portions of the strap which contact treated lumber, and optionally, the interior portions of nail holes 1705. Partial coating of strap 1703 reduces cost and weight of the strap. Partial coating also allows spray and brushing application techniques for manufacture. Although a hurricane strap is shown in FIGS. 17 and 18, the methods and structure of this invention may be applied to any metallic structural component such as joist hangars, post supports, and other metallic straps, supports and hangars used in the art.

Still other embodiments of the invention utilize addition of structural, corrosion inhibitor or biological inhibitor fillers to the resins used in the coatings of FIGS. 17 and 18. For example, conductive fillers having high anodic potential may be added to the resins before curing to provide anodic protection of the structural component itself. Or, reinforcing fillers and fibers such as graphite or glass fibers may be added for increased structural strength of the coating. Or, in still other embodiments, biocides or fungicides may be added to the resin to reduce biological or fungicidal degradation at the joints utilizing the components of this invention. The use of these and other fillers may also be applied to the resins used in manufacture of the inserts described in FIGS. 1-16.

Although the description above contains many specifications, these should not be construed as limiting the scope of the invention but merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

1. A corrosion protection insert for metallic construction supports used in attaching a treated lumber, said insert comprising: a semi-rigid body of a polymeric material, said body comprising a predefined shape wherein at least two orthogonal insert attachment surfaces of said insert fit between corresponding support attachment surfaces of said construction support and corresponding treated lumber attachment surfaces.
 2. The corrosion protection insert of claim 1 wherein said insert comprises an attachment means for attaching said insert to said construction support.
 3. The corrosion protection insert of claim 2 wherein said attachment means is a tab on said insert that engages said construction support.
 4. The corrosion protection insert of claim 3 wherein said tab comprises a J-shaped cross section to engage an edge of said construction support.
 5. The corrosion protection insert of claim 3 wherein said tab comprises a L-shaped cross section to frictionally engage an edge of said construction support.
 6. The corrosion protection insert of claim 2 wherein said attachment means is a male fastener element engageable with a complementary element on said construction support.
 7. The corrosion protection insert of claim 7 wherein said male fastener element is a button tab and said complementary element is a nail hole on said construction support.
 8. The corrosion protection insert of claim 2 wherein said attachment means comprises a pressure-sensitive adhesive disposed on said body of said insert.
 9. The corrosion protection insert of claim 2 wherein said attachment means is an interference fit with said construction support.
 10. The corrosion protection insert of claim 2 wherein said insert is a cured resin and said attachment means is a resin bond to said construction support.
 11. The corrosion protection insert of claim 9 wherein said insert is a joist hangar insert comprising a generally U-shaped body having an interference fit with inside U-shaped surfaces of a joist hangar.
 12. The corrosion protection insert of claim 1 wherein said construction support is a joist hangar wherein said at least two surfaces of said insert comprise a generally U-shaped portion and a perpendicular back plate surface.
 13. The corrosion protection insert of claim 12 wherein said back plate surface comprises a slot between two legs of said generally U-shaped portion.
 14. The corrosion protection insert of claim 1 wherein said construction support is a hurricane strap wherein said at least two surfaces of said insert define an elongated body comprising a first surface at a first end of said body and a second surface, perpendicular to said first surface and disposed at a second end of said body.
 15. A corrosion protection construction support for use with treated lumber, said support comprising: a metallic body comprising at least two orthogonal attachment surfaces for attaching said treated lumber; and a polymeric film attached to said metallic body whereby said film separates said metallic body and said treated lumber thereby preventing corrosion of said metallic body.
 16. The corrosion protection construction support of claim 15 wherein said polymeric film is a cured resin bonded to said at least two attachment surfaces.
 17. The corrosion protection construction support of claim 16 wherein said polymeric film is a semi-rigid polymeric insert attached to said metallic body.
 18. The corrosion protection construction support of claim 15 wherein said metallic body is a joist hangar.
 19. The corrosion protection construction support of claim 15 wherein said metallic body is a hurricane strap.
 20. The corrosion protection construction support of claim 15 wherein said metallic body is a post support.
 21. A method of reducing corrosion of metallic construction supports used with treated lumber, the method comprising the step of placing a semi-rigid, preformed polymeric insert having at least two orthogonal surfaces between joining surfaces of said treated lumber and said metallic construction support.
 22. Said method of claim 21 wherein said insert is placed in said construction support before assembly of said treated lumber and said construction support.
 23. Said method of claim 21 wherein said insert is engaged to said construction support after assembly of said construction support and a first joining surface of a first treated lumber. 